Method header

public function header($function, &$options)
{
    if ($function == '') {
        return false;
    }
    $function = strtolower($function) . 'Header';
    if (!is_callable(array($this, $function))) {
        throw new \InvalidArgumentException('Function ' . $function . ' not supported', 500);
    }
    return call_user_func_array(array($this, $function), array(&$options));
}